Detectives have launched an investigation into an electronic listening device that was allegedly planted outside actress Nicole Kidman's (search) Sydney mansion, police said Tuesday.

The device was found near a security car that was monitoring Kidman's home from the street, chief bodyguard Neil McMaster told Sydney's The Daily Telegraph for its Tuesday edition.

He said he believed the device was intended to intercept conversations between the Australian-born Oscar-winning actress and her bodyguards outside the mansion.

McMaster said surveillance footage taken from the house provided "conclusive evidence" that the device had been intentionally planted.

The bug was apparently discovered when security officers searched the grounds early Sunday in preparation for Kidman's return to Sydney to film her new movie, "Eucalyptus." (search)

If identified, the eavesdropper could be charged with illegal use of a telecommunications devise and trespassing.

Kidman has been pursued by eavesdroppers in the past. Paparazzo Eric Ford recorded a telephone conversation in 1998 between Kidman and her then husband Tom Cruise (search) and sold it to the U.S. newspaper The Globe.